Medication intended for injection into the patient is often stored in vials. Vials are small, typically glass, containers having an open mouth covered by a rubber membrane or diaphragm. The rubber diaphragm is held in place by a metal ring. The rubber diaphragm is initially covered by a cap which is removed prior to use, typically with a flicking action of one's thumb. Presently, the usual procedure for drawing medicine into a syringe for subsequent injection into a patient involves the following steps: (1) The diaphragm of the vial containing medication is cleaned, usually with an alcohol swab; (2) A capped or sheathed needle is affixed to a syringe and the needle's sheath is removed; (3) The vial is often inverted so that the medicine is in contact with the diaphragm; (4) Frequently, an amount of air approximately equal to the amount of medication intended to be drawn up is then aspirated into the syringe; (5) The needle is inserted through the diaphragm into the vial; (6) The air that was aspirated into the syringe is pushed into the vial to prevent a vacuum that would make it more difficult to draw up the medicine; (7) The medicine is aspirated into the syringe; (8) The needle is removed from the vial; (9) The medicine is either injected into the patient or the needle is recapped for later injection.
Some potential problems with preparing medications for injection are contamination of the medication and accidental injury from the needle. Needle injuries generally involve puncturing one's finger during manipulation of the syringe and vial or while recapping the needle.